Many activated homogeneous polymerization or oligomerization catalysts are very effective to produce liquid polyolefins for many applications, such as lubricant base stocks, functional fluids, adhesives, as well as intermediates used for further functionalization, etc. For all these applications, the catalyst components must be removed to below certain specification level (usually less than 10 ppm) before its next step or for applications. Catalyst removal is typically accomplished by first deactivating the catalyst followed by multi-stage washing with water followed by one or more separation steps to remove all the catalyst components. The washing step usually includes several stages of mixing with aqueous dilute acid/base wash and further settling/separation steps. See U.S. Pat. Nos. 6,960,700; 6,706,828, 7,060,768 and 5,705,577. There are also numerous aqueous work up procedures reported in the literature.
These prior art methods suffer particularly by being cumbersome and more importantly are difficult and expensive to scale up for commercial operation. They also generate a large amount of waste. Still more importantly, they are often not effective to reduce the metal content when the product is liquid polyolefins. Generally, when producing solid polyolefins by metallocene or other polymerization catalyst technology the catalyst residual is not an issue and is usually left in the product. However, in liquid polyolefins production, the catalyst residual generally must be removed, especially when the next step in the process is hydrogenation, functionalization, or for typical end use applications of liquid polyolefins, such as for lubrication formulations, personal care products or functional fluids. The presence of catalyst residual deactivates the hydrogenation catalyst, inhibits the functionalization reaction, and introduces impurities in the finished product which maybe detrimental for performance of the finished product.
The present inventors have discovered an efficient and effective method to remove polymerization catalyst residual by using a solid sorbent, which can interact chemically and/or physically with the catalyst components and/or the deactivated catalyst component. The method according to the present invention is particularly effective when scaled up to commercial operations.